Spinning machines or the like are generally provided with hoods for the aspiration of such floating matter. The particle-laden air is drawn by a blower into a raw-air compartment of a filter box separated by a screen from a clean-air compartment which has an outlet for the discharge of the filtered air. This air flow results in the progressive accumulation of solids on the entrance side of the screen, i.e. on its surface confronting the raw-air compartment, which impedes the filtering operation; thus, the screen will have to be cleaned from time to time. Conventional filter boxed do not provide ready access to the screen for that purpose.